_Bornite_ (Erubescite, Peacock copper ore), 3Cu_{2}S.Fe_{2}S_{3},
occurring in Cornwall, which passes with depth into chalcopyrite.
_Tetrahedrite_ (Fahl ore), a very complex sulphide of copper, iron,
lead, zinc, with arsenic, etc. It is often rich, and carries silver
values.
=Oxidised Ores.=—The most important of the oxidised ores are—
_Malachite_, CuCO_{3}.Cu(OH)_{2}, containing, when pure, 57·3 per
cent. copper (73·7 CuO); is widely distributed, but usually occurs as
such in non-paying quantities except in a few particular localities. It
is found in the upper parts of the veins. Whenever found with sulphide
ores, it is an extremely useful material to mix in the charge, as it
supplies oxygen as well as copper. Malachite is still an important
source of the metal in Mexico, Chili, and Bolivia, though not quite so
much so as formerly, whilst it is specially important in the Tanganyika
(Katanga) deposits, of which it constitutes the greater portion so far
developed.
_Cuprite_, Cu_{2}O, contains 88·8 per cent. copper, when pure. It is
widely distributed, but is never found by itself in paying deposits,
though in the early days of mining and smelting it was an important
source of metal, since it was easily reduced, and consequently was
cheaply worked.
_Melaconite_, CuO, contains 79·8 per cent. copper, when pure; is fairly
widely distributed, although hardly ever in sufficient quantity to pay.
In one or two localities, however—viz., Tennessee, North Carolina, and
Virginia—it was formerly an important source of the metal. The deposits
were at first very promising, as they consisted largely of very rich
melaconite ore; this was however, quickly worked out, the ordinary
heavy chalcopyrite with 2·5 per cent. copper being struck below.